Self-Balance Control of Electric Unicycle Based on Active Disturbance Rejection Control

For self-balance control of electric unicycle (EU), the conventional PID control often leads to poor dynamic performance. In this paper, an active disturbance rejection control (ADRC) based control design approach is proposed to improve the control performance. Firstly, the dynamic model of unicycle is explored, which builds up the fundamental relation between the input and output, namely motor output torque and the attitude pitch angle. Since the physical model is nonlinear and highly sensitive to external conditions such as the system load, a sophisticated control strategy is required for practical usage. To this end, a three-level cascaded control system is designed, which is composed of the current loop, the motor speed loop, and the attitude loop, respectively. The former two loops are for speed regulation of the unicycle, while the third loop controls the attitude based on the ADRC to deal with various uncertainties. The control performance is verified through simulation studies along with comparisons with the conventional PID control. Results show that the ADRC-based control system achieved better self-balance for attitude control, where the attitude adjustment period is shortened and the overshot of the attitude is also reduced.